JP2001284618A - Solar cell, its manufacturing method and watch using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell structure which can drive an electronic device without lowering a generating voltage even in a state that a part of the solar cell is shaded and lights do not impinge thereon; its manufacturing method; and a watch structure as the electronic device using the same. SOLUTION: This solar cell comprises a plurality of element arrays which are linearly formed via predetermined intervals on a transparent insulation layer provided on a metal substrate, and the element array has solar cell elements in which a lower electrode provided on the transparent insulation layer, a generating layer and an upper electrode are sequentially laminated; a transparent insulation film formed so as to coat the solar cell elements; the upper electrode via an opening part of the transparent insulation film; and a connection electrode provided so as to connect the lower electrode of the adjacent solar cell elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a solar cell as a primary battery of electronic equipment, and more particularly to a structure of a solar cell for driving a wristwatch, a method of manufacturing the same, and a structure of a timepiece. It is.

[0002]

2. Description of the Related Art Electronic devices using a solar cell as a primary battery are increasing in order to eliminate the hassle of battery replacement and as a clean energy source that does not pollute the global environment. As an example of the electronic device, a wristwatch including a secondary battery will be described.

[0003] Since the electromotive force of a general solar cell is low to drive a wristwatch equipped with a secondary battery, it is usually used by connecting a plurality of stages in series to increase the generated voltage. A conventional solar cell structure connected in four stages in series will be described with reference to FIG. FIG. 5 is a plan view showing a conventional solar cell.

In FIG. 5, a solar cell has four fan-shaped solar cell elements 52 formed on a disc-shaped transparent substrate 50 having a central hole 56. Although not shown in FIG. 5, the solar cell element 52 includes a transparent substrate 50
The lower electrode 57, the power generation layer 58, and the upper electrode 59 are sequentially laminated on the upper electrode 57.

[0005] The upper electrode 59 of each solar cell element 52 and the lower electrode 57 of the adjacent solar cell element 52 are connected by a connection electrode 53, so that four stages of electromotive force can be obtained in series. I have. The electromotive force is output terminal 5
5 Here, the first output terminal 55a is a lower electrode of the solar cell element 52a, and the second output terminal 5a
5b is an upper electrode of the solar cell element 52d.

Here, the transparent substrate 50 is made of glass,
The lower electrode 57 is made of indium tin oxide having high light transmittance, and the upper electrode 59 is made of a Ti film. The power generation layer 53 is made of amorphous silicon, and is pi from the transparent substrate 50 side.
It has an n-diode structure. Then, power is generated by light incident on the power generation layer 13 from the transparent substrate 50 side.

When incorporated in a wristwatch equipped with a secondary battery, it is placed on a dial through an hour wheel driving an hour hand through a center hole 56. At this time, the connection electrode 53a
Are arranged in the direction of 12:00 and the connection electrode 53c is oriented in the direction of 6 o'clock.

[0008]

However, wristwatches tend to cast shadows on cuffs and the like, so that in such a configuration, a situation in which light does not hit a part of the solar cell is likely to occur. For example, when the left half of the wristwatch is shadowed by the cuffs, light does not shine on half the area of the conventional solar cell shown in FIG. 5, and only the other half generates power. In such a state, the number of stages for power generation is reduced, and only a power generation voltage of two stages in series is obtained, so that the secondary battery cannot be charged.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a solar cell capable of driving an electronic device without lowering the generated voltage even when a part of the solar cell is shaded and is not exposed to light. It is an object of the present invention to provide a structure, a manufacturing method thereof, and a timepiece structure as an electronic device using the same.

[0010]

Means for Solving the Problems In order to achieve the above object, a solar cell of the present invention and a method for manufacturing the same employ the following means.

[0011] The solar cell of the present invention comprises a plurality of element rows linearly formed at predetermined intervals on a transparent insulating layer provided on a metal substrate having a smooth surface, and the plurality of element rows are arranged in parallel. A solar cell having a transparent protective film provided on the element array and the common electrode, wherein the element array has a lower electrode provided on the transparent insulating layer, and a power generation layer provided on the lower electrode. A plurality of solar cell elements including an upper electrode provided on the power generation layer, a transparent insulating film formed so as to cover the solar cell element, and an upper electrode adjacent to the upper electrode through an opening of the transparent insulating film. A connection electrode provided to connect the lower electrode of the solar cell element.

A solar cell according to the present invention is characterized in that a plurality of solar cell elements constituting each element row are connected in series.

The solar cell according to the present invention is characterized in that, in a plurality of solar cell elements constituting an element array, the areas thereof are substantially equal.

According to the method for manufacturing a solar cell of the present invention, a step of forming a transparent insulating layer on a metal substrate, a step of forming a lower electrode,
Forming a power generation layer, forming an upper electrode to form a solar cell element, forming a transparent insulating film so as to cover the same, forming a connection electrode, and forming a transparent protective film. It is characterized by having.

In such a solar cell configuration in which a plurality of solar cell elements connected in series are connected in parallel, even if a part of the solar cell is not exposed to light. In addition, the electronic device can be driven without generating voltage drop.

This is because each of the element rows to which the light is applied is constituted by a plurality of solar cell elements connected in series, so that even if the power generation area is reduced, the number of stages in series connection does not change and the power generation voltage does not change. Is not going down.

In the solar cell of the present invention incorporated in a wristwatch equipped with a secondary battery, even when part of the solar cell is not exposed to light, the generated voltage does not decrease. It can be carried out.

In the solar cell according to the present invention, the color of the power generation layer of the solar cell element is perceived by the naked eye by reducing the line width of the linearly formed element row with respect to the interval between adjacent element rows. become unable. Therefore, a solar cell having almost the same appearance as a metal substrate on which no solar cell element is formed can be obtained.

Further, in the solar cell of the present invention, power is generated by light incident from the upper electrode side. Then, of the light incident on the power generation layer from the upper electrode side, the light that reaches the metal substrate without being absorbed by the power generation layer is reflected by the metal substrate and passes through the power generation layer again. Absorption amount of
Power generation efficiency is improved.

In the solar cell of the present invention, the color of the power generation layer cannot be perceived by the naked eye, and its appearance is almost the same as that of a metal substrate on which no solar cell element is formed. It does not impose any restrictions on the appearance or design of the watch. Therefore, the appearance of the watch does not deteriorate.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a solar cell according to the best mode for carrying out the present invention will be described below with reference to the drawings.

In the present invention, a wristwatch equipped with a secondary battery is assumed as an electronic device, and the best solar cell structure for driving a wristwatch equipped with a secondary battery will be described. Furthermore, in this specification, a solar cell element is a lower electrode, a power generation layer,
An element in which the upper electrode is sequentially stacked. An element row is a linear 1 in which a plurality of solar cell elements are connected in series.
One book. The term “solar cell” refers to an entire structure including a metal substrate, a transparent insulating layer, a plurality of element rows formed thereon, a plurality of common electrodes, and output terminals. In addition, the series connection of the solar cell elements will be described by taking a four-stage connection as an example.

(Description of Solar Cell Structure of First Embodiment: FIGS. 1, 2, and 3) The solar cell structure will be described with reference to FIGS. 1, 2, and 3. FIG. FIG. 1 is a plan view showing a solar cell according to the present embodiment.

In FIG. 1, a solar cell comprises a disk-shaped metal substrate 10 and a transparent insulating layer 1 formed thereon.
1, a semicircular first common electrode 21 a, a semicircular second common electrode 21 b, a plurality of element rows 24 including a plurality of solar cell elements 22, and an output terminal 25. .

The first common electrode 21a and the second common electrode 2
1b is arranged along the circumference of the metal substrate 10,
Facing each other. The first common electrode 21a and the second common electrode 21a
In the circle inside the common electrode 21b, a plurality of element rows 2
4 are arranged side by side. The linear element row 24 includes 12
Although shown in the figure, there are actually 100 or more.

In order to clarify the positional relationship, the structure of the element array 24 is shown in a simplified manner, but each element array 24 is composed of the first solar cell element 22a and the second solar cell element 22a. The solar cell element 22b, the third solar cell element 22c, and the fourth solar cell element 22d are formed by connecting four stages in series in a straight line. The two ends of the plurality of element rows 24 are the first
Are connected to the common electrode 21a and the second common electrode 21b. Therefore, a plurality of element rows 24 are electrically connected to the common electrode 21 in parallel.

Furthermore, a first output terminal 25a is formed on the first common electrode 21a, and a second output terminal 25a is formed on the first common electrode 21a.
A second output terminal 25b is formed at b. As described above, the solar cell according to the present embodiment has a structure in which a plurality of element rows 24 that can obtain outputs in four stages in series are connected in parallel, and sufficient power is obtained to drive a wristwatch equipped with a secondary battery. It has become.

Next, the configuration of the element array 24 will be described with reference to FIGS. FIG. 2 shows the first common electrode 2
It is the detail of the planar structure of 1a, 1st solar cell element 22a, and 2nd solar cell element 22b. FIG. 3 shows element row 2
4 is a cross-sectional view in the longitudinal direction of FIG.

In FIG. 3, a solar cell element 22 includes a lower electrode 12 formed on a transparent insulating layer 11 provided on a metal substrate 10 and a power generation layer 13 formed on the lower electrode 12.
And the upper electrode 14 formed on the power generation layer 13 are sequentially laminated.

A transparent insulating film 15 is formed so as to cover the periphery of the solar cell element 22, and the transparent insulating film 15 has a contact hole 15 for making a connection with the connection electrode 23.
a is formed. Here, the transparent insulating film 15 has a role of preventing the lower electrode 12 and the upper electrode 14 of the same solar cell element 22 from being short-circuited.

The upper electrode 14 of the first solar cell element 22a and the lower electrode 12 of the second solar cell element 22b are connected by a connection electrode 23 to form a series connection.
Similarly, the second solar cell element 22b to the fourth solar cell element 22d are connected in series by the connection electrode 23, and
The element row 24 is formed.

The connection between the first common electrode 21a and the element array 24 is performed by connecting the first common electrode 21a to the first solar cell element 22.
The lower electrode 12 of FIG. The connection between the second common electrode 21b and the element row 24 is made by connecting the second common electrode 21b to the fourth solar cell element 22d.
Are connected by the connection electrode 23.

Further, a transparent protective film 16 is formed on the whole except for the output terminal 25. This transparent protective film 16
It plays a role in preventing defects caused by damage to the solar cell.

The solar cell according to the present embodiment has an upper electrode 14
It is configured to generate power using light incident from the side. Here, the metal substrate 10 is Kovar which is an alloy of iron, nickel and cobalt, and the transparent insulating layer 11 has a thickness of 1 μm to 20 μm.
Glass layer. Kovar used as the metal substrate 10 has substantially the same thermal expansion coefficient as the glass layer as the transparent insulating layer 11. Therefore, it is possible to prevent the glass layer from being damaged and peeled off due to a temperature rise of the metal substrate in a manufacturing method described later.

The lower electrode 12 and the upper electrode 14 are made of indium tin oxide (hereinafter referred to as ITO) having high light transmittance. The power generation layer 13 is made of amorphous silicon and has a p-type of 5 to 20 nm from the transparent insulating layer 11 side,
It has a stacked diode structure of i-type of 0 to 1000 nm and n-type of 10 to 100 nm.

Further, the connection electrode 23 is also made of an IT having high light transmittance.
It is made of O. The transparent insulating film 15 is silicon nitride. The transparent protective film 16 is made of a silicone resin.

The solar cell according to the present embodiment has an upper electrode 14
Power is generated by light incident from the side. Then, the upper electrode 14
Of the light that has entered the power generation layer 13 from the side and has reached the metal substrate 10 without being absorbed by the power generation layer 13,
Since the light is reflected at 0 and passes through the power generation layer 13 again, the amount of light absorbed by the power generation layer 13 increases, and the power generation efficiency improves.

With respect to the interval between adjacent element rows 24,
By reducing the line width of the linear element row 24, the color of the power generation layer 13 of the solar cell element 22 cannot be perceived by the naked eye. Thereby, the external appearance of the solar cell of the present embodiment is the metal substrate 1 on which the solar cell element 22 is not formed.
It is almost the same as 0.

According to the experiment, the solar cell having the shape shown in FIG.
In order to obtain a sufficient amount of power generation to drive a wristwatch equipped with a secondary battery at an illumination intensity of 500 lx of a normal fluorescent lamp, and to make the color of the power generation layer 13 invisible to the naked eye,
In the case of a metal substrate 10 of φ30, the line width of the element row 24 is 5 μm to 2 μm.
0 μ, the distance between adjacent element rows 24 is 100 μ to 8
0μ. The appearance of the solar cell at this time is almost the same as that of the metal substrate 10 on which the solar cell element 22 is not formed.

The first common electrode 21a and the second common electrode 2
The line width of 1b is 200 μm to 700 μm, which is considerably wider than the element row 24. This is because the resistance value needs to be low in order to connect the plurality of element rows 24 in parallel.

The first common electrode 21a is also the second common electrode 2
1b is also made of ITO having high light transmittance, so that its color is not perceived by the naked eye even if the line width is widened. Further, when actually being incorporated in an electronic device, each common electrode 21 may be hidden by the case of the electronic device.

(Description of Manufacturing Method of Solar Cell of First Embodiment) Next, a manufacturing method for forming a solar cell structure of the present embodiment will be described with reference to FIGS.

The metal substrate 10 is made of Kovar which is an alloy of iron, nickel and cobalt. As shown in FIG. 6, a liquid applied glass film (SOG) is formed on the entire surface of the metal substrate 10 by a spin coating method. Then, from 300 ° C to 400
A baking treatment is performed at a temperature of ° C. to evaporate the solvent contained in the applied glass film, thereby forming a glass layer as the transparent insulating layer 11.

This transparent insulating layer 11 is formed with a thickness of 1 μm to 20 μm. With a thin film of 1 μm or less, a short circuit occurs between the metal substrate 10 and the lower electrode 12 due to a pinhole. In order to eliminate pinholes, it is desirable to form the film with a thickness of 1 μ or more. The film thickness can be controlled by adjusting the number of rotations in the spin coating method or the amount of solvent contained in the coated glass film to adjust the viscosity of the coated glass film.

Next, as shown in FIG.
An ITO is formed on the entire surface as the lower electrode 12 to a thickness of 100 nm by a sputtering method.

The sputtering conditions at this time are as follows: 100 sccm argon gas and 2 sccm
Oxygen gas is introduced, the pressure is adjusted to 70 mPa to 4 Pa, and a high frequency power of 0.5 to 3 kW is applied to the ITO target.

Further, a photoresist 41 is formed on the lower electrode 12 and patterned into a pattern of the solar cell element 22 and the common electrode 21. Next, as shown in FIG. 7, the lower electrode 12 is dry-etched using the photoresist 41 as a mask pattern. Thereafter, the photoresist 41 is stripped.

At this time, the dry etching conditions were as follows: a hydrogen bromide gas was introduced into the dry etching apparatus at 100 sccm, and the pressure was adjusted to 1 Pa to 10 Pa.
To 0, a high-frequency power of 1 kW to 3 kW is applied.

Next, as shown in FIG. 8, amorphous silicon is used as the power generation layer 13 and pi is applied from the transparent insulating layer 11 side.
It is formed by a plasma CVD method so as to have an n-type diode structure.

The conditions for forming the p-type amorphous silicon at this time are as follows.
A diborane gas of 0.1 sccm and 0.1 sccm to 1 sccm is introduced, the pressure is adjusted to 50 Pa to 300 Pa, and a high frequency power of 50 W to 300 W is applied to the counter electrode. Then, a film having a thickness of 10 nm is formed.

The conditions for forming i-type amorphous silicon are as follows: silane gas 100 sccm in a plasma CVD apparatus.
Is introduced, the pressure is adjusted to 50 Pa to 300 Pa, and high frequency power of 50 W to 300 W is applied to the counter electrode. Then, a film having a thickness of 500 nm is formed.

The conditions for forming the n-type amorphous silicon are as follows: silane gas 100 sccm in a plasma CVD apparatus.
And a phosphine gas of 0.1 to 1 sccm are introduced, the pressure is adjusted to 50 Pa to 300 Pa, and 50 W
A high-frequency power of 300 W is applied. And a film thickness of 20 nm
Form.

Further, ITO is formed to a thickness of 100 nm as the upper electrode 14 by a sputtering method. The sputtering conditions at this time are such that 100 sccm of argon gas and 2 sccm of oxygen gas are introduced into the sputtering apparatus, the pressure is adjusted to 70 mPa to 4 Pa, and a high-frequency power of 0.5 to 3 kW is applied to the ITO target.

Further, a photoresist 42 is formed on the upper electrode 14, and is patterned into a pattern of a solar cell element. Next, as shown in FIG.
2 as a mask pattern, the upper electrode 14 and the power generation layer 13
Is continuously dry-etched. Then, the photoresist 42 is removed.

At this time, the dry etching conditions for the ITO, which is the upper electrode 14, are set to 10 in the dry etching apparatus.
0 sccm of hydrogen bromide gas is introduced and the pressure is 1 Pa to 1
The pressure is adjusted to 0 Pa, and high-frequency power of 1 kW to 3 kW is applied to the metal substrate 10.

The dry etching conditions for the amorphous silicon as the power generation layer 13 are as follows.
A sulfur hexafluoride gas of 00 sccm to 300 sccm and a chlorine gas of 10 sccm to 100 sccm are introduced, the pressure is adjusted to 0.5 Pa to 20 Pa, and a high-frequency power of 100 W to 1 kW is applied to the metal substrate 10.

Next, as shown in FIG.
As No. 5, a silicon nitride film is formed to a thickness of 300 nm by a plasma CVD method.

The conditions for forming silicon nitride at this time are as follows:
A silane gas of 20 sccm and a nitrogen gas of 100 sccm to 500 sccm are introduced into the plasma CVD apparatus, the pressure is adjusted to 50 Pa to 300 Pa, and 50 W to
A high-frequency power of 100 W is applied. And a film thickness of 300 n
m.

Further, a photoresist 43 is formed on the transparent insulating film 15 and is patterned into a pattern having a contact hole 15a. Next, as shown in FIG. 11, the transparent insulating film 15 is dry-etched using the photoresist 43 as a mask pattern. Then, the photoresist 43 is removed.

The conditions for dry etching of the silicon nitride as the transparent insulating film 15 are as follows: 100 sccm to 300 sccm of sulfur hexafluoride gas and 10 sccm to 100 sccm of chlorine gas are introduced into the dry etching apparatus, and the pressure is set to 0.5 Pa to The pressure is adjusted to 20 Pa, and high-frequency power of 100 W to 1 kW is applied to the metal substrate 10.

Thereafter, as shown in FIG.
As No. 3, ITO is formed to a thickness of 200 nm by a sputtering method. The sputtering conditions at this time are such that 100 sccm of argon gas and 2 sccm of oxygen gas are introduced into the sputtering apparatus, the pressure is adjusted to 70 mPa to 4 Pa, and a high-frequency power of 0.5 to 3 kW is applied to the ITO target.

Further, a photoresist 44 is formed on the connection electrode 23 and is patterned into a connection electrode pattern. Next, as shown in FIG.
Is used as a mask pattern, the connection electrode 23 is dry-etched. Then, the photoresist 44 is removed.

At this time, the dry etching conditions for the ITO as the connection electrode 23 are set to 10 in the dry etching apparatus.
0 sccm of hydrogen bromide gas is introduced and the pressure is 1 Pa to 1
The pressure is adjusted to 0 Pa, and high-frequency power of 1 kW to 3 kW is applied to the metal substrate 10.

Thereafter, as shown in FIG.
Is formed, and a solar cell is completed.
The transparent protective film 16 can be omitted.

(Description of Timepiece to which Solar Cell of First Embodiment is Applied) Next, the structure of a wristwatch provided with a secondary battery as an electronic device using the solar cell of the present embodiment will be described. The solar cell according to the present embodiment shown in FIGS. 1, 2 and 3 is used for a dial of a wristwatch. FIG. 14 is a partial cross-sectional view of the wristwatch in the 3 o'clock-9 o'clock direction. Hereinafter, description will be made with reference to FIG. 1, FIG. 3, and FIG.

As shown in FIG. 14, a watch case 8 provided with a windshield 83 made of transparent glass or sapphire.
A movement 87 is provided in 5. This movement 87 drives a pointer 89.

Although not shown in FIG. 14, in the movement 87, a secondary battery for storing the electromotive force of the solar cell, a quartz oscillator as a time reference source, and an oscillation frequency of the quartz oscillator are used. In addition, a semiconductor integrated circuit that generates a drive pulse for driving a timepiece, a step motor that receives and receives the drive pulse, a wheel train mechanism that transmits the movement of the step motor to a pointer, and the like are provided.

The crown 86 has a function of adjusting the time by moving the hands 89. When the crown 86 is pulled, the hands 89 stop. By turning the crown 86 while pulling the crown 86, the hands 89 can be moved and the time can be set.

A windshield glass 83 is attached to the watch case 85 via a second packing 99 made of a resin material, and has a hermetically sealed structure for preventing dust, moisture and moisture from entering the watch.

Further, a groove is provided on the surface of the watch case 85 opposite to the windshield 83, and a first packing 97 made of a rubber material is provided in the groove. The first packing 97 arranged between the back cover 95 and the watch case 85 has an airtight and airtight structure for preventing dust, moisture and moisture from entering the watch.

On the dial 81, a transparent insulating layer 11, a plurality of element rows 24 including a plurality of solar cell elements 22, a common electrode 21, and a transparent protective film 1 are formed on a metal substrate 10.
6 is used. Further dial plate 81
Is placed on the movement 87.

At this time, the orientation of the solar cell is
Is installed so that it is aligned with the direction from 12:00 to 6:00.
This is to prevent the power generation voltage of the solar cell from lowering even if it becomes a shadow such as a cuff.

The dial 81 is provided with a center hole for projecting an hour wheel driving an hour hand, an hour pin driving a minute hand, a second hand driving a second hand, and the like. On the surface of the dial 81, time scales, characters and marks are provided as time display means.

The middle frame 93 has a movement 87 and a dial 81.
Are held in the watch case 85, and the middle frame 93 is made of a resin material. Then, the dial 81 and the movement 87 are stored in the opening of the watch case 85 via the middle frame 93.

Then, the end face of the middle frame 93 holding the dial 81 and the movement 87 on the side opposite to the windshield 83 is pressed with the back cover 95, so that the dial 81 is attached to the watch 91 and the watch case 85. They are in contact as if pressing.

The watch 91 covers the outer peripheral area of the dial 81 and plays a role as a decorative plate of a timepiece. The watch 91 can be made of a material different from that of the watch case 85, or the surface of the watch 91 can be ground using a diamond tool, and the surface can be mirror-finished to increase the value of the watch as a decorative product. Is increasing. Although not shown in FIG. 14, the cutout 91 also covers the common electrode 21 on the dial 81. Therefore, the common electrode 21 is not visible from the outside.

Although not shown in FIG. 14, the output terminals 25a and 25b of the solar cell and the movement 87 are electrically connected.

In the solar cell according to the present embodiment, the color of the power generation layer 13 cannot be perceived with the naked eye and is substantially the same in appearance as the metal substrate on which the solar cell element 22 is not formed. Incorporation into the watch has no effect on the appearance or design of the watch. Therefore, the appearance of the watch does not deteriorate.

Since the inside of the timepiece has a hermetically sealed structure, the transparent protective film 16 of the solar cell may be omitted.

(Explanation of a Mechanism for Charging the Solar Cell of the First Embodiment to a Secondary Battery) The solar cell of the present embodiment has the structure described above, and further has the structure described above. In a wristwatch equipped with a secondary battery,
Even in a state where light does not shine on a part of the solar cell, there is an effect that the secondary battery can be charged without lowering the generated voltage. The reason will be described below.

First, a mechanism for generating electricity from a solar cell and charging a secondary battery will be described with reference to FIGS. FIG. 15 is a schematic diagram of a charging circuit of a wristwatch including a secondary battery, and FIG. 16 is a graph illustrating an operating voltage and an operating current when the solar battery charges the secondary battery.

In FIG. 15, a current i (A) flows from the solar battery 61 to the secondary battery 62, and charges the secondary battery 62. Then, the clock circuit 64 is driven by the voltage charged in the secondary battery 62. The backflow prevention diode 63 has a role of preventing a current from flowing from the secondary battery 62 to the solar battery 61 side.

As is apparent from FIG. 15, the solar cell 61
Is the voltage of the secondary battery 62 and the backflow prevention diode 6.
3 is equal to the sum of the voltages. From this, the solar cell 6
The operation voltage and the operation current when charging the secondary battery 62 from 1 can be obtained from the voltage-current characteristics of the solar cell 61 and the backflow prevention diode 63.

In FIG. 16, a curve 71 represents a solar cell 61.
The curve 72 shows the voltage-current characteristic of the backflow prevention diode 63 on which the voltage of the secondary battery 62 is superimposed. The intersection 66 of the curve 71 and the curve 72 is the operating point of the solar cell for charging. That is, the voltage of the solar cell 61 is V0 (V), and the current I0 (A) flows through the secondary battery 62 to perform charging.

A mechanism for charging a secondary battery when the solar cell of this embodiment shown in FIG. 1 is applied to a wristwatch with the structure shown in FIG. 14 will be described with reference to FIG. In addition,
It is assumed that the wristwatch has the charging circuit shown in FIG.

In FIG. 17, a curve 72 represents the secondary battery 62.
7 shows voltage-current characteristics of the backflow prevention diode 63 on which the above-mentioned voltage is superimposed. A curve 75 shows a voltage-current characteristic of the solar cell when the entire surface of the solar cell of the present embodiment shown in FIG. As described above, curves 75 and 7
The intersection 67 of 2 is an operating point for charging the secondary battery 62 from the solar cell of the present embodiment shown in FIG.

Therefore, when light is applied to the entire surface of the solar cell of this embodiment shown in FIG.
At (V), the current I1 (A) flows to the secondary battery 62 to perform charging.

In the solar cell according to the present embodiment, the secondary cell 62 can be charged even if light does not hit the entire surface. For example, when half of the wristwatch is shadowed by cuffs and the like, and only half shines, light does not shine on the left half area of the solar cell of the present embodiment shown in FIG. 1 but only on the right half area. This corresponds to the case where light hits. As shown in FIG.
In the solar cell of this embodiment, each of the element rows 24 has a configuration of four stages in series. Therefore, even if the power generation area is halved, a voltage of four stages in series is obtained, and the generated voltage is reduced. Absent.

In the solar cell of this embodiment shown in FIG. 1, the voltage-current characteristics when power is generated in half the area are shown in FIG.
The curve 76 of FIG. In the curve 76, the generated current is reduced, but the generated voltage is not reduced. Then, an intersection 68 with the curve 72 becomes an operating point at which the secondary battery 62 is charged.

Therefore, when light is applied to half the area of the solar cell of the present embodiment shown in FIG. 1 to generate power, the current I2 (A) is increased by the voltage V2 (V) of the solar cell.
2 and charge.

As a comparative example, the operating point of the conventional solar cell shown in FIG. 5 will be described with reference to FIGS. 5, 15 and 18. As described above, the conventional solar cell shown in FIG. 5 is incorporated in a wristwatch with the connection electrode 53a arranged in the 12 o'clock direction and the connection electrode 53c arranged in the 6 o'clock direction. It is assumed that the wristwatch has the charging circuit shown in FIG.

For example, if the left half of the wristwatch is shadowed by the cuffs, light does not shine on half the area of the conventional solar cell shown in FIG. 5, and only the other half generates power. In such a state, the number of power generation stages is reduced, and only two series of power generation voltages can be obtained.

In FIG. 18, a curve 72 represents the secondary battery 62.
7 shows voltage-current characteristics of the backflow prevention diode 63 on which the above-mentioned voltage is superimposed. A curve 77 is a voltage-current characteristic when light is applied to the entire surface of the conventional solar cell in FIG. 5 to generate power, and a curve 78 is generated when light is applied to half the area of the conventional solar cell in FIG. It is a voltage-current characteristic at the time.

Although the curve 77 has an intersection 69 with the curve 72, the curve 78 and the curve 72 have no intersection. This means that the secondary battery 62 can be charged when power is generated by irradiating the entire surface of the conventional solar cell shown in FIG. 5 with light, but only when half of the area of the conventional solar cell shown in FIG. If not, it indicates that the secondary battery 62 cannot be charged.

In the conventional solar cell shown in FIG. 5, when light shines only on half the area, only two stages of power generation voltages can be obtained in series. Since the power generation voltage of the solar cell is lower than the sum of the voltage of the secondary battery 62 and the voltage of the backflow prevention diode 63, the secondary battery 62 cannot be charged.

(Description of Structure of Modification of First Embodiment: FIG. 4) The structure of the solar cell will be described with reference to FIG. FIG.
FIG. 4 is a plan view showing a solar cell according to a modification of the first embodiment.

Referring to FIG. 4, a solar cell comprises a metal substrate 10 having a rectangular shape and a transparent insulating layer 11 provided thereon.
, A first linear common electrode 31 a, a second linear common electrode 31 b parallel to the first common electrode 31 a, a plurality of element rows 24 including a plurality of solar cell elements 22, and an output terminal 35. .

The first common electrode 31a and the second common electrode 3
1b are arranged along opposing sides of the metal substrate 10 and face each other. First common electrode 31a
And a plurality of element rows 2 inside the second common electrode 31b.
4 are arranged side by side. The linear element row 24 includes 12
Although shown in the figure, there are actually 100 or more. Further, in order to clarify the positional relationship, the configuration of the element row 24 is illustrated in a simplified manner.

The structure of the element array 24 is exactly the same as that of the first embodiment, and the description is omitted. In addition, the function and effect of making the color of the power generation layer invisible is the same, and thus the description is omitted. Then, the method of manufacturing the solar cell according to the present embodiment and the first method
The manufacturing method of the solar cell according to the embodiment is the same, and the description is omitted. Further, the configuration incorporated in a wristwatch equipped with a secondary battery and the charging mechanism for the secondary battery are the same as those in the first embodiment, and thus description thereof will be omitted.

In the solar cell according to the present embodiment, even when a part of the solar cell is not exposed to light, the electronic device can be driven without a decrease in the generated voltage.

This is because each of the element rows 24 to which light is applied is constituted by a plurality of solar cell elements 22 connected in series, so that even if the power generation area is reduced, the number of stages in series connection does not change. This is because the generated voltage does not decrease.

Further, in the solar cell of this embodiment, a rectangular metal substrate 10 is used. Since the first common electrode 31a and the second common electrode 31b are arranged in parallel, the lengths of the element rows 24 arranged therebetween are equal. That is, the generated current of each element row 24 becomes equal.

Therefore, in a state where a part of the solar cell according to the present embodiment is shaded and no light is applied to the plurality of element arrays 24, even if any of the element arrays 24 is shaded, the generated current decreases. Is constant, the current supplied to the electronic device is stabilized.

In the above description, the series connection of the solar cells of the present invention has been described in four stages. However, the invention is not limited to four stages, and a voltage and a voltage sufficient for driving the electronic equipment to be used.
Any number of stages may be used as long as a current can be obtained.

If the electronic equipment used is highly confidential and moisture and dust do not enter, the transparent protective film 16 of the solar cell of the present invention may be omitted.

Although the metal substrate 10 has been described in Kovar,
Other metal materials and alloy materials such as K material and brass may be used. Alternatively, a metal substrate having a single-layer or multilayer surface treatment, such as a gold-plated SK material, may be used.

Although the transparent insulating layer 11 has been described as a glass layer,
Other materials may be used as long as they have high light transmittance and high insulation. It may be a transparent oxide such as SiO2, a transparent nitride such as Si3N4, or a transparent resin. Examples of the transparent resin include polyester, polyamide, and polystyrene.

The lower electrode 12, the upper electrode 14, and the connection electrode 23 are not limited to ITO as transparent electrodes, but may be S electrodes.
nO2, ZnO or the like may be used. The power generation layer 13 may be made of polycrystalline silicon, cdSe, or the like. Further, the power generation layer 13 has been described as having the pin diode structure when viewed from the transparent insulating layer 11 side, but the ni is viewed from the transparent insulating layer 11 side.
A p-diode structure may be used.

Since the power is generated by making light incident from the upper electrode 14 side, the lower electrode 12 may be a metal film having no light transmission property.
It may be a membrane.

Although the transparent insulating film 15 has been described by using silicon nitride, it may be made of a transparent oxide such as silicon oxide or a transparent resin such as polyethylene. Also, the transparent protective film 16
May be a transparent resin such as polyethylene, a transparent oxide such as silicon oxide, or a transparent nitride such as silicon nitride.

The coated glass film as the transparent insulating layer 11 can be formed by a printing method, a dipping method in which the metal substrate 10 is immersed in a coating glass solution, or a method using a roll, in addition to the spin coating method. Can also be formed.

The method for forming the lower electrode 12, the upper electrode 14, and the connection electrode 23 is not limited to sputtering, and a general film forming method such as vapor deposition can be used. The etching may be performed by wet etching. For example, when the lower electrode 12 is made of ITO, etching is performed with a mixed solution of iron oxide, hydrochloric acid, and water such that the mixing ratio is 3: 5: 2.

[0113]

As is apparent from the above description, in the solar cell of the present invention, even when a part of the solar cell is not exposed to light, the power generation voltage does not decrease and the electronic device is driven. be able to.

This is because each of the element rows to which light is applied is constituted by a plurality of solar cell elements connected in series, so that even if the power generation area is reduced, the number of series-connected stages does not change and the power generation voltage does not change. Is not going down.

In the solar cell of the present invention incorporated in a wristwatch equipped with a secondary battery, even when part of the solar cell is not exposed to light, the generated voltage does not decrease. It can be carried out.

In the solar cell of the present invention, the color of the power generation layer of the solar cell element can be perceived by the naked eye by reducing the line width of the linearly formed element row with respect to the interval between adjacent element rows. become unable. Therefore, it is possible to obtain a solar cell having almost the same appearance as a metal substrate on which no solar cell element is formed.

In the solar cell of this embodiment, power is generated by light incident from the upper electrode side. Then, of the light incident on the power generation layer from the upper electrode side, the light that reaches the metal substrate without being absorbed by the power generation layer is reflected by the metal substrate and passes through the power generation layer again. And the power generation efficiency is improved.

In the solar cell of the present invention, the color of the power generation layer is not perceptible to the naked eye, and the appearance is almost the same as that of a metal substrate on which no solar cell element is formed. It does not impose any restrictions on the appearance or design of the watch. Therefore, the appearance of the watch does not deteriorate.

[Brief description of the drawings]

FIG. 1 is a plan view of a solar cell according to an embodiment of the present invention.

FIG. 2 is a plan view of the solar cell according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view of the solar cell according to the embodiment of the present invention.

FIG. 4 is a plan view of a solar cell according to a modification of the embodiment of the present invention.

FIG. 5 is a plan view showing a conventional solar cell.

FIG. 6 is a cross-sectional view illustrating the method of manufacturing the solar cell according to the embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.

FIG. 10 is a cross-sectional view illustrating the method of manufacturing the solar cell according to the embodiment of the present invention.

FIG. 11 is a cross-sectional view illustrating the method of manufacturing the solar cell according to the embodiment of the present invention.

FIG. 12 is a cross-sectional view illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.

FIG. 13 is a cross-sectional view illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.

FIG. 14 is a partial cross-sectional view showing a timepiece to which the solar cell according to the embodiment of the present invention is applied.

FIG. 15 is a schematic diagram of a charging circuit of a wristwatch including a secondary battery.

FIG. 16 is a graph showing operating voltage and current of a solar cell.

FIG. 17 is a graph showing operating voltage and current of the solar cell according to the embodiment of the present invention.

FIG. 18 is a graph showing operating voltage and current of a conventional solar cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Metal substrate 11 Transparent insulating layer 21 Common electrode 22 Solar cell element 24 Element row 25 Output terminal

Claims (5)

[Claims] An element array linearly formed on a transparent insulating layer provided on a metal substrate at a predetermined interval, a common electrode connecting the element arrays in parallel, and a common electrode with the element array. A solar cell having a transparent protective film provided on an electrode, wherein the element row is a solar cell element in which a lower electrode, a power generation layer, and an upper electrode provided on the transparent insulating layer are sequentially stacked, and the solar cell A transparent insulating film formed so as to cover the element, and an upper electrode through an opening of the transparent insulating film,
A connection electrode provided to connect a lower electrode of an adjacent solar cell element. 2. The solar cell according to claim 1, wherein the solar cell elements are connected in series. 3. The solar cell according to claim 1, wherein the areas of the solar cell elements are substantially equal. 4. An element array linearly formed at predetermined intervals on a transparent insulating layer provided on a metal substrate, a common electrode connecting the element arrays in parallel, and a common electrode with the element array. A solar cell having a transparent protective film provided on an electrode, wherein the element row includes a solar cell element in which a lower electrode, a power generation layer, and an upper electrode provided on the transparent insulating layer are sequentially laminated, and the solar cell element A transparent insulating film formed so as to cover the
A method of manufacturing a solar cell, comprising: an upper electrode through an opening of the transparent insulating film, and a connection electrode provided to connect a lower electrode of an adjacent solar cell element, A step of forming a transparent insulating layer on a metal substrate,
Forming a lower electrode, forming a power generation layer, forming an upper electrode, and forming a solar cell element; forming a transparent insulating film so as to cover the solar cell element, forming a connection electrode; A method for manufacturing a solar cell, comprising a step of forming a film. 5. A timepiece comprising a case having a windshield, a movement for driving hands, and a dial, wherein the dial is provided at a predetermined interval on a transparent insulating layer provided on a metal substrate. An element array formed in a linear shape through a common electrode that connects the element array in parallel, and a solar cell having a transparent protective film provided on the element array and the common electrode are formed. A solar cell element in which a lower electrode, a power generation layer, and an upper electrode provided on the transparent insulating layer are sequentially laminated; a transparent insulating film formed so as to cover the solar cell element; and an opening in the transparent insulating film A timepiece using a solar cell, comprising: an upper electrode via a portion; and a connection electrode provided to connect a lower electrode of an adjacent solar cell element.